My dream would be a star wars game like this and supremacy where you could build empires, a campaign would take weeks to finish, you could custom build destroyers and super star destroyers with different modules, some carry more troops, others are like gun platforms, other hold thousands of x wings. Huge space battles can take hours with reinforcements on the way, every engagement needing to be planned, the ability to seem in and see little details on the ships, weakening destroyer shields and sending in troops to board and cause distruption, capturing ships to take home and convert, etc. Not all battles ending in destuction of the enemy, some even making you leave as to regroup and come back later.
etc